METHOD FOR PRODUCTION OF WATER-SOLUBLE PURIFIED HYDROXYETHYLCELLULOSE Russian patent published in 1999 - IPC

FIELD: paper-and-pulp industry. SUBSTANCE: cellulose is treated with aqueous sodium hydroxide solution to form alkaline cellulose that is further subjected to hydroxyethylation with gaseous ethylene oxide at elevated temperature. Resultant alkaline hydroxyethylcellulose is neutralized, washed, and dried. According to invention, hydroxyethylation is carried out in two steps: first, 40-45 wt % of liquid ethylene oxide is added to alkaline hydroxyethylcellulose and temperature of reaction mixture is adjusted to 60-80 C, after which the rest of ethylene oxide is added in the form of circulating gas-vapor mixture containing about 70 vol % of gaseous ethylene oxide, at least 30 vol % of inert gas, and water vapor to 100 vol %. Furthermore, hydroxyethylation reaction is carried out at temperature close to 100 C; neutralization is carried out in two steps: first, 18-22% aqueous solution of sodium phosphate salts is added to achieve pH value of suspension 9-11, after which 2.0-2.5 kg/kg of cellulose are separated from liquid phase. To concentrated suspension, orthophosphoric acid is added to achieve pH 2-3 and suspension is treated with glyoxal. EFFECT: simplified process. 4 cl, 1 dwg, 1 tbl, 5 ex